CamTim: Hacking a camera remote for time-lapse photography
CamTim is a simple electronic circuit hack that allows any digital camera (with a remote) to be used for time-lapse photography of nature (moonrises or sunsets for example), continuous shooting of an event or for monitoring applications including research and security applications etc.
CamTim can also be used in an external trigger mode, where the trigger can come from a wireless source (using ZigBee modules) or from an external sensor operating on TTL voltages. This is especially handy for bird and wildlife photography.
So how does the CamTim work?
The CamTim consists of a set of switches to select the camera delay, a microcontroller to read the switch values and generate a pulse train, and an interface circuit to periodically close the camera's remote switch.
Switches in the CamTim board are set to select the camera trigger delay from 20us to 40 minutes (the maximum delay is customizable to several days). A microcontroller (PIC16F84A) reads the switch settings and loops indefinitely to trigger a solenoid that then triggers the camera's remote control. Note that an amplifier is required to drive the solenoid and a diode is required across the solenoid to prevent back-emfs from reaching the mcu. A good design should probably include an opto-coupler to isolate the mcu from the solenoid.
Once the electronics and code is complete, its a simple matter to open the camera's remote control, and find out where the PCB traces from the switch go. In the adjoining figure, the two connections of the camera switch are tapped near the black chip near the bottom right corner of the PCB (click on image to enlarge).
Afterword: A cheaper solution is probably to use a 555 chip. But the 555 solution suffers from many problems including poor adaptibility and inability to create anything other than simple square wave pulse trains at a single frequency. On the other hand, a mcu-based solution such as this would allow a variety of frequencies, would relieve the user of the burden of carrying a bunch of resistances or a multi-meter to measure one and calculate the time-period. Furthermore, complex pulse patterns can be programmed into the mcu. For example, a pulse-train with an arithmetic progression of delays is an easy reach. Crucially, the mcu can be used to interface with wireless devices for remote triggering and with sensors for proximity triggering.
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